Galvanic nickel bath for depositing silk-dull nickel coats

ABSTRACT

A galvanic nickel bath for precipitating silk-dull nickel coats, which includes anion active primary and/or secondary phosphoric acid esters of polyalkylene oxide adducts adapted to be produced from ethylene oxide and/or propylene oxide and/or butylene oxide, or of the salts of such propylene oxide adducts.

United States Patent 11 1 1111 3,865,702 Immel et al. Feb. 11, 1975 1 GALVANIC NICKEL BATH FOR 2,986,500 5/l96l Passal 204/49 DEPOSITING SILKJDULL NICKEL COATS 3,084,111 4/1963 Strauss et a1 204/49 X Inventors: Waldemar lmmel, Solingen;

Wennemar Strauss, Erkrath-Unterbach, both of Germany Dr. W. Kampschulte & Cie, Solingen, Germany Filed: Feb. 21, 1973 Appl. No.: 334,298

Assignee:

References Cited UNITED STATES PATENTS 4/1943 Lind et al. 204/49 Primary ExaminerG. L. Kaplan Attorney, Agent, or Firm-Walter Blecker [57] ABSTRACT A galvanic nickel bath for precipitating silk-dull nickel coats, which includes anion active primary and/or secondary phosphoric acid esters of polyalkylene oxide adducts adapted to be produced from ethylene oxide and/or propylene oxide and/or butylene oxide, or of the salts of such propylene oxide aclducts.

3 Claims, N0 Drawings GALVANIC NICKEL BATH FOR DEPOSITING SlLK-DULL NICKEL COATS The present invention relates to a galvanic nickel bath for precipitating dull, glare or dazzle free nickel coats with a certain content of basic luster substances. The production of articles the surface of which is made glare-free by the galvanic precipitation of silk-dull nickel coats is to an ever increasing extent requested by consumers in a wide range of technical fields. A silkdull nickel coat is characterized by a velvet-like luster and by a reduced reflection as compared to nickel coats having a high luster and strong reflection.

It is known to produce such silk-dull coats by mechanical treatment of the surface of the respective article either prior to or following the deposit of a lustrous strongly reflecting coat by dulling. Thevarious heretofore known drawbacks of this method have been overcome by the manufacture of galvanic nickel baths which make it possible to obtain the precipitation of silk-dull coats directly out of the bath. In this connection there are to be distinguished such nickel baths to which insoluble pulverous particles are added which will be enclosed in the otherwise smooth nickel coat thereby producing a rough velvet like surface, from nickel baths which contain organic additions which result in a dull shiny deposit of nickel with reduced reflecting ability.

With the last mentioned galvanic nickel baths it is known to add non-iongenic alkylene oxide adducts to galvanic nickel baths of customary composition having a content of basic luster substances. In this connection the bath contains such substituted or non-substituted ethylene oxide or propylene oxide or ethylene oxidepropylene oxide adducts in a concentration of from 5 100 mg/l which at a temperature of from 40 75C form a finely dispersed emulsion in the bath electrolyte. These addition compounds include, for instance, the high molecular polyethylene oxides, polypropylene oxides, mixing adducts of ethylene oxide and propylene oxide, addition compounds of ethylene oxide and propylene oxide or ethylene oxide and propylene oxide in any desired sequence on one or multi-valent saturated and unsaturated straight chained and branch chained aliphatic, cycloaliphatic, aromatic and heterocyclic-alcohols, ethyl hydrosulfides (mercaptanes), aldehydes, ketones, acetals, amines, carbonic acids, carbonic acid amides and phenols.

Furthermore the composition of the customary nickel baths is known which consists of nickel salts, such as nickel chloride, nickel sulfate, nickel fluorborate or nickel sulfamate and customarily contains a buffer, such as boric acid. A frequently employed bath is the so-called Watt-bath with nickel chloride, nickel sulfate and boric acid.

With these known galvanic nickel baths for a direct precipitation of silk-dull coats of the type described above, the drawback has been encountered that on the one hand there exists the danger that the satin former, when operating with air, will float and that in addition thereto with profiled and greatly curved workpieces in certain current density ranges no uniform deposit can be obtained. Inasmuch as the articles which are to be provided with a nickel coat are in most instances profiled, so that for this reason extremely low current densities occur during the galvanizing process, the resulting lack of uniformity of the coat represents a rather important drawback. Above all, at low current densities, with the heretofore known baths involved, dark and up to black deposits are obtained which sometimes appear only as dots but sometimes also cover extensive areas. This is true in particular for the current density range below 1 Amp/dm It is, therefore an object of the present invention to provide a galvanic nickel bath for depositing silk-dull nickel coats which, even at low current densities, will assure the production of a proper uniform coat while the precipitation of dark deposits onto the articles to be galvanized will be avoided.

These objects have been realized according to the present invention by the fact that the galvanic nickel bath contains anionactive primary and/or secondary phosphoric acid esters of polyalkylene oxide adducts adapted to be produced from ethylene oxide and/or propylene oxide and/or butylene oxide, or :by the fact that the galvanic nickel bath contains the salts of such polyalkylene oxide adducts. I

The present invention concerns the teaching that anionactive primary and secondary phosphoric acid esters of polyalkylene oxide adducts prepared by the known reaction of polyalkylene adducts and P 2 O 5 when added to nickel baths containing basic luster substances, especially nickel baths of the Watt-type, during the galvanizing process will yield silk-dull nickel deposits. By polyalkylene oxide adducts intended for reaction with P 2 O there are meant addition compounds of ethylene oxide, propylene oxide, butylene oxide or mixtures of these alkylene oxides in any desired sequence with low molecular organic compounds. such a ethyleneglycol, propyleneglycol, ethyleneglycol, etc., which with reference to active hydrogen represent bior polyfunctional low molecular organic compounds.

Preferably, the galvanic nickel bath according to the invention contains the phosphoric acid esters in a con centration of from 20 8O mg/l.The galvanic nickel bath according to the present invention makes possible the generation of a silky luster on articles in the form of a uniform coat even when low and very low current densities are involved. Black deposits do not occur so that above all with highly profiled and curved workpieces to be coated considerable advantages are realized by the present invention over the state of the art as it existed prior to the invention.

From the numerous phosphoric acid esters which may be used in connection with the generation of a silky luster in a nickel bath, there may be mentioned the following EXAMPLE To a nickel bath of the Watt-type which as basic luster substance contains 1 g/l of saccharin, there are added 40 mg/l of a mixture of primary and secondary phosphoric acid esters which mixture was obtained by reaction of the adduct of 30 mol propylene oxide and 30 mol ethylene oxide on propyleneglycol with P 2 O 5 in a molar ratio (mean with regard to P 2 O of 2.5 l as high viscous, higher molecular liquid. When galvanizing in the range of from 0.5 5 Amp/dm 2 at a temperature of 60C bath temperature, silk-dull nickel deposits of maximum uniformity were obtained on polished brass. With a layer or coat thickness of IO um, the peak-to-valley height of the nickel amounted to 0.25

pared by reacting the adduct of 30 mol propylene oxide and 30 mol ethylene oxide on propylene glycol with P 0 5 at a mol ration of 2.5:].

2. A galvanic nickel bath according to claim 1, which contains 1 g/l of saccharin.

3. A galvanic nickel bath according to claim 1, in which the bath contains nickel salts selected from the group consisting of nickel chloride, nickel sulfate nickel fluorborate and nickel sulfamate. 

1. A GALVANIC AQUEOUS, ACIDIC BATH FOR PRECIPITATNG SILK-DULL NICKEL COATS, CONTAINING ACTIVE PHOSPHORIC ESTERS IN CONCENTRATION OF 20-80 MG/L, WHICH ARE PREPARED BY REACTING THE ADDUCT OF 30 MOL PROPYLENE OXIDE AND 30 MOL ETHYLENE OXIDE ON PROPYLENE GLYCOL WITH P2O5 AT A MOL RATION OF 2.5:1.
 2. A galvanic nickel bath according to claim 1, which contains 1 g/1 of saccharin.
 3. A galvanic nickel bath according to claim 1, in which the bath contains nickel salts selected from the group consisting of nickel chloride, nickel sulfate, nickel fluorborate and nickel sulfamate. 